Method and apparatus for closing tubes

ABSTRACT

A bottom in a tube having an open end is formed by heating the tube and a supporting mandrel and advancing a sleeve over the end of the tube which flares outwardly after heating so as to collapse the flared end. The collapsed end of the tube is closed by contacting the collapsed end with a mold which cooperates with the sleeve to form the bottom.

This is a continuation of application Ser. No. 770,786, filed Feb. 22,1977, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to closing thermoplastic tubes having an open endso as to form a tube bottom from the material of the previously openended tube.

It is known that the end of an open tube comprising a thermoplasticmaterial may be closed without attaching a separate piece to form thebottom. U.S. Pat. No. 2,876,496--Murphy, Jr. discloses a method andapparatus for closing an open ended tube at one end by initially heatingthe end so as to flare the end outwardly. A sleeve is then advanced overthe flared end to collapse the outwardly flared end. Subsequently, amandrel is inserted into the tube and a die or mold cooperates with thetube and the sleeve to close the collapsed end. There is no heating ofthe mandrel which is inserted into the tube prior to closing. It issignificant that the patent only discloses the closing of small sizetubes, e.g., catheter tubing having an internal diameter of 0.190inches.

U.S. Pat. No. 3,300,559--Baehr also discloses a method and apparatus forclosing the open end of thermoplastic tubes. The open end of the tubewhich is mounted on a mandrel is brought into contact with a cup-likemember. A heating element is then brought into heating engagement withthe cup-like member on the side opposite the open end while the mandrelcarrying the tube is advanced so as to collapse and close the end of thetube. The heating member is then retracted while the tube remains incontact with the cup-like member. The cup-like member is then cooled andthe closed tube is subsequently retracted from the cooled cup-likemember. There is no heating of the mandrel.

U.S. Pat. No. 3,509,252--Baehr discloses a method and apparatus similarto that disclosed in the aforesaid Baehr patent except that the cup-likemember is heated directly. The cup-like member does not necessarilycompletely close the end of the tube. Rather complete closing of the endof the tube to achieve the finished bottom shape is provided by anothercup-like member which is relatively cool. Neither Baehr patent disclosesthe heating of the mandrel heated in advance of contact by a cup-likemember.

SUMMARY OF THE INVENTION

It is an overall object of this invention to provide an improved methodand apparatus for closing open-ended tubes.

It is a more specific object of this invention to provide a method andapparatus for closing thermoplastic tubes which may have substantialdiameters.

It is another specific object of this invention to provide a method andapparatus for closing thermoplastic tubes in a rapid and efficientmanner.

It is a still further specific object of this invention to provide amethod and apparatus for closing thermoplastic tubes in a reliablemanner.

It is a still further specific object of this invention to provide amethod and apparatus for closing thermoplastic tubes so as to assureattractive closed tubes.

In accordance with these and other objects, an open-ended thermoplastictube is supported on a mandrel extending longitudinally into the tubewhile heating the mandrel and the tube simultaneously so as to flare theend of the open-ended tube outwardly away from the heated mandrel. Theflared end of the tube is then collapsed by contact with a telescopingsleeve surrounding the open-ended tube and the mandrel. The collapsedend is then closed to form the bottom of the tube by contacting thecollapsed end by a mold which is substantially cooler in temperaturethan the mandrel and forming the bottom over the end of the heatedmandrel. The mold may then be separated from the bottom and the mandreland the mandrel subsequently separated from the newly-formed tube bottomand removed from the tube.

In accordance with one important aspect of the invention, the mandreland the open-ended tube are heated radiantly from the source locatedadjacent the open end of the tube. Preferably, the tube and the mandrelare heated substantially longer than the mold contacts the collapsed endof the tube. It is also desirable to heat the sleeve simultaneously withthe mandrel and to advance the sleeve during heating so as to optimizethe collapsing of the flared end.

In accordance with another important aspect of the invention, aplurality of open-ended tubes are simultaneously supported by aplurality of mandrels respectively. Preferably, the plurality of tubessupported by the plurality of mandrels are simultaneously heated,subsequently and simultaneously heated and collapsed and subsequentlyand simultaneously closed. Where the open-ended tubes are supported by aplurality of mandrels, it is preferred to contact the collapsed ends ofthe tubes with a resiliently mounted mold so as to compensate forvarying lengths of tubes.

In order to simultaneously support the tubes on a plurality of mandrels,a turret may be provided comprising a plurality of mandrels located ateach of a plurality of positions on the turret. The steps of heating,heating and collapsing and closing may then be accomplished at aplurality of stations located around the turret.

A BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 are sectional views depicting a plurality of steps in theprocess of closing open-ended tubes in accordance with this invention;and

FIG. 5 is a plan view showing a turret for closing a plurality ofopen-ended tubes during high speed manufacturing.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

As shown in FIG. 1, an open-ended tube 10 has been mounted on a mandrel12 as an initial step in a tube closing operation. The mandrel 12comprises an annular shoulder 14 which is abutted by the end of the tube10 when supported on the mandrel 12. A sleeve 16 surrounds the tube 10with the end of the tube 10 which is to be closed extending outwardlybeyond the end of the sleeve 16 and the end of the mandrel 12 which areseparated by a distance substantially less than the maximumcross-sectional dimension or diameter of the tube.

In FIG. 2, the tube 10 as well as the mandrel 12 and the sleeve 16 areheated from a radiant source located opposite and adjacent the end ofthe mandrel 12, the tube 10 and the sleeve 16. The source as shown inFIG. 2 comprises a gas flame 18 which produces an outward flaring 20 atthe end of the tube 10.

As shown in FIG. 3, the sleeve 16 is advanced while the tube 10, mandrel12 and tube 16 continue to be heated so as to collapse the end of thetube 10 in the area 22. Sleeve 16 may be advanced by various means. Asshown, a spring 24 is provided between an anchoring point 26 and an arm28. Initially and during the steps depicted by FIGS. 1 and 2 (the springhas been eliminated in these figures for the sake of simplicity), thespring 24 is maintained under tension while the arm 28 is latched inplace in a position abutting the shoulder 14 of the mandrel. Then, inFIG. 3, the arm 28 is unlatched so as to drive the sleeve 16 forward tothe telescoped position shown in FIG. 3.

As shown in FIG. 4, a mold assembly 30 is advanced to a position ofcontact with the end of the sleeve 16 and the collapsed portion 22 ofthe tube 10 so as to close the tube 10 and form a bottom 32. At thistime, the spring 24 attached to the sleeve 16 is again placed undertension which assures that the sleeve 16 is held in contact with themold assembly 30 to properly form the bottom 32.

The mold assembly 30 comprises two separate sections. A sleeve section34 has an internal diameter which permits it to slide over the externaldiameter of tube 10 in contact with the end of the sleeve 16. A centralmolding section 36 with a slightly concave surface 37 contacts thecollapsed portion 22 of the tube 10 so as to form the bottom 32. It willbe noted that a spring 38 is provided between the molding section 36 andthe end 39 of the molding assembly 30 so as to accommodate a variationin the thickness of the bottom 32 which might result from a longer orshorter tube 10. After closing the end of the tube 10, the moldingassembly 30 may be and is retracted almost immediately as will besubsequently described in connection with FIG. 5.

In accordance with this invention, the mandrel 12 is heatedsimultaneously with the tube 10 and the sleeve 16 so as to permit theend of the mandrel 12 to serve as a molding surface which cooperateswith the relatively cool molding assembly 30. It has been found that theheating of the mandrel 12 so as to permit its use as a molding surfacepermits large-size tubes to be closed. For example, it is possible toclose tubes as large as two inches in diameter. Furthermore, thetechnique provides a very rapid closing of the tube while at the sametime producing an attractive product. The speeds with which the ends maybe closed is in part attributable to the fact that the molding assembly30 is not heated, or is at least relatively cool as compared with themandrel 12 so that it may be separated immediately upon closing the endof the tube 10. Simultaneously with the retraction of the mold assembly30 and the separation from the bottom 32, the mandrel 12 begins to coolin preparation for the ejection of the tube 10 from the mandrel 12.

Reference will now be made to FIG. 5 wherein apparatus is shown forachieving a high state of production of tubes having closed ends. Asshown in FIG. 5, a turret 40 comprises a plurality of mandrel sets 42which are adapted to rotate through a plurality of stations a-f.

At station a, a plurality of tubes 10 are fed onto a set of the mandrels12. The turret 40 is then advanced to the first heating station bwherein a gas heater 18₁ heats the tubes 10, the mandrels 12 not shownand the sleeves 16. The turret 40 is next advanced to the next heating cwherein the gas heater 18₂ radiantly heats the tube 10, the mandrels 12not shown and the sleeves 16. At position d, a gas heater 18₃ continuesto heat the tubes 10, the mandrels 12 and the sleeves 16. However, thesleeves 16 are now advanced so as to collapse the open end of the tubes10. At station e of the turret, the mold assemblies 30 for each of theplurality of mandrels 12 not shown, are advanced so as to form theclosed ends 32 of the tubes and subsequently retracted. Next, themandrels 12 are advanced to station f where the tubes 10 with the closedbottoms 32 are ejected or extracted from the mandrels 12.

As clearly demonstrated by FIG. 5, the heating of the mandrels 12 ratherthan the molding assembly 30 permits the molding surface provided by theends of the mandrels 12 to reach the necessary high temperature withoutdelaying the closure process. In this connection, it will be understoodthat a molding surface which is too warm may not be separated from thebottom 32 without altering or distorting it. It will be noted that themandrels 12 have time to cool, i.e., from the time of closing at statione to the time when they reach station f. In fact, cooling has begun whenthe mandrels 12 leave station d. On the other hand, if the heating wereachieved through the molding assembly 30 and the mold sections 36provided the heated molding surface, cooling of the molds prior toseparation from tubes 10 would require that the turret remainsufficiently long at each position so as to allow the molds of theassembly 30 to cool after closing and before the assembly 30 isretracted. This of course increases the time which must be allotted foreach position of the turret 40 and thereby delays the tube closureprocess.

FIG. 5 also depicts the relatively long period of time that the mandrelsand the tubes 10 are heated as compared with time taken to close theends of the tubes to form the bottoms 32. In this regard, it will benoted that the tubes are heated through stations b-d of the turret 40whereas tube closing takes place only at station e. In this way, themandrels 12 are able to reach a very high temperature so as to assurethe effectiveness of the molding surface provided by those mandrels 12in preparation for their function at station e when the ends of thetubes are closed. Also note that the resilient mounting of the moldingsection 36 is particularly important to accomodate the various lengthsof tubes 10 which may be mounted on the mandrels of a single set.

It will be appreciated that the method and apparatus disclosed hereinmay be utilized with a variety of thermoplastic materials. For example,tubes may be closed in accordance with this invention wherein the tubescomprise cellulose butyrate, polypropylene, nylon, Teflon andpolyethylene. It will also be appreciated that the necessarytemperatures which must be achieved from the heaters 18₁, 18₂ and 18₃will vary as a function of the particular thermoplastic material and thedwell time at each station. In this manner, temperature control of theheating of the tubes is attained in the embodiment heretofore described.

Although a particular embodiment of the invention has been shown anddescribed, it will be understood that other modifications may be madewithout departing from the true spirit and scope of the invention as setforth in the appended claims. For example, the high speed manufactureachieved by the turret approach might also be achieved by mounting aseries of mandrels on a conveyor which is associated with moving workstations positioned along the conveyor. It will also be appreciated thatthe molding surface need not comprise a mandrel which supports the tubebut may comprise another member which is inserted into the tube andheated. It will also be understood that the invention does notnecessarily require that the mold outside the tube as contrasted withthe molding surface inside the tube be unheated. In fact, it may bedesirable with certain materials to heat the mold. Note further, thatthe mold has been characterized herein as concave although it may alsobe flat or convex.

What is claimed is:
 1. A method of manufacturing a plastic tube having abottom formed from an open-ended tube without using additional materialfor forming the bottom comprising the following steps:supporting theopen-ended tube on a mandrel extending longitudinally into said tube;heating said mandrel and said tube simultaneously so as to flare the endof the open-ended tube outwardly away from the heated mandrel;collapsing said flared end by contact with a sleeve surrounding saidopen-ended tube and said mandrel and telescopically movable relativethereto; heating said mandrel and said tubes while collapsing saidflared end; closing said collapsed, previously flared end to form saidbottom by contacting said collapsed end with a mold which issubstantially cooler in temperature than said mandrel and forming saidbottom over the end of said mandrel; separating said mold from saidformed bottom and said mandrel; and separating said mandrel from saidtube after said mold has been separated from said bottom and saidmandrel.
 2. The method of claim 1 wherein said mandrel and saidopen-ended tube are heated radiantly.
 3. The method of claim 2 whereinsaid mandrel and said open-ended tube are heated radiantly from a sourcelocated adjacent said mandrel end.
 4. The method of claim 1 wherein saidtube and said mandrel are heated substantially longer than said moldcontacts said collapsed end of said tube.
 5. The method of claim 1wherein said sleeve is heated simultaneously with said mandrel and saidopen-ended tube.
 6. The method of claim 5 wherein said mandrel, saidsleeve, and said open-ended tube are heated radiantly from a sourcelocated adjacent said mandrel end.
 7. The method of claim 1 wherein theopen end of said tube opposite said collapsed end rests on a shoulder ofsaid mandrel.
 8. The method of claim 1 wherein said mold resilientlycontacts said collapsed end.
 9. The method of claim 8 wherein the openend of said tube opposite said collapsed end rests on a shoulder of saidmandrel.
 10. The method of claim 9 wherein said mandrel and saidopen-ended tube are heated radiantly from a source located adjacent saidmandrel end.
 11. The method of claim 1 further comprising the step ofcooling said mandrel while closing said collapsed end.
 12. The method ofclaim 1 wherein a plurality of said open-ended tubes are simultaneouslysupported by a plurality of mandrels respectively.
 13. The method ofclaim 12 wherein said open-ended tubes on said mandrels are sequentiallyheated and closed.
 14. The method of claim 13 wherein said tubes areheated and collapsed prior to closing.
 15. The method of claim 14wherein said open-ended tubes on said mandrels are simultaneouslyheated, simultaneously heated and collapsed and simultaneously closed.16. A method of manufacturing a plastic tube having a bottom formed froman open-ended tube without using additional material for forming thebottom comprising the following steps:heating the open-ended tube so asto flare the end outwardly; collapsing the flared end; closing thecollapsed, previously flared end to form said bottom against a heatedmolding surface located on the interior of the tube; and further heatingthe end after flaring and before closing.
 17. The method of claim 16wherein the temperature of said molding surface is controlled.
 18. Themethod of claim 16 wherein the bottom is also formed against a moldlocated on the exterior of the tube.
 19. The method of claim 18 whereinthe temperature of the mold on the exterior is controlled independentlyfrom the temperature of the molding surface on the interior.
 20. Amethod of manufacturing a plastic tube having a bottom formed from anopen-ended tube without using additional material for forming the bottomcomprising the following steps:supporting the open-ended tube between amandrel and a sleeve; heating said mandrel, said sleeve and said tubesimultaneously so as to flare the end of the open-ended tube outwardlyaway from the heated mandrel with the end of the mandrel being separatedfrom the end of said sleeve a distance substantially less than themaximum cross-sectional dimension of the tube; collapsing said flaredend by contact with said sleeve surrounding said open-ended tube andsaid mandrel and being telescopically movable relative thereto; closingsaid collapsed, previously flared end to form said bottom by contactingsaid collapsed end with a mold; separating said mold from said formedbottom and said mandrel; and separating said mandrel from said tubeafter said mold has been separated from said bottom and said mandrel.21. The method of claim 20 wherein substantial contact between theflared end and the sleeve is avoided.
 22. The method of claim 20 whereinthe tube is flared outwardly a distance substantially greater than thethickness of the sleeve.
 23. The method of claim 20 whereinsubstantially all of the end of said tube extending beyond said mandreland said sleeve is flared outwardly.
 24. The method of claim 20 whereinsaid mandrel is at least partially cylindrical and the end of saidsleeve is substantially aligned with the end of the cylindrical portionof said mandrel.
 25. A method of manufacturing a plastic tube having abottom formed from an open ended tube without using additional materialfor forming the bottom comprising the following steps:supporting theopen ended tube between a mandrel and a sleeve the end of said sleevebeing substantially aligned with the end of the cylindrical portion ofsaid mandrel; heating said mandrel, said sleeve and said tubesimultaneously so as to flare the end of the open ended tube outwardlyaway from the heated mandrel, the tube being flared outwardly a distancesubstantially greater than the thickness of the sleeve; collapsing saidflared end by contact with said sleeve surrounding said open ended tubeand said mandrel said sleeve being telescopically movable relativethereto; closing said collapsed previously flared end to form saidbottom by contacting said collapsed end with a mold; separating saidmold from said formed bottom of said mandrel; and separating saidmandrel from said tube after said mold has been separated from saidbottom and said mandrel.
 26. The method of claim 25 wherein substantialcontact between the flared end and the sleeve is avoided.
 27. The methodof claim 25 wherein the end of the mandrel is separated from the end ofthe sleeve during the flaring of said tube a distance substantially lessthan the maximum cross sectional dimension of the tube.
 28. The methodof claim 25 wherein substantially all of the end of said tube extendingbeyond said mandrel and said sleeve is flared outwardly.